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[McIDAS #OXG-395498]: conversion of lac level1b to area format

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  • Subject: [McIDAS #OXG-395498]: conversion of lac level1b to area format
  • Date: Thu, 03 Jan 2008 13:09:32 -0700
Hi Marc,

re: how to use IR imagery to determine cloud base/top heights

> Going back to this statement, would I be able from, Mcidas V, determine the 
> cloud base/top
> height once I determine the temperature of the layer of clouds in the image 
> by using a
> profile of temperatures? I was thinking of this just in case I have trouble 
> from my friend's
> analyses.

I would say that you could "estimate" the cloud top height (or pressure) using 
the
observed infrared temperature if you know the vertical profile of temperatures 
in
the atmosphere near the cloud you are interested in.  I say estimate since the
energy seen from the satellite is not from a specific part of the cloud.  
Rather,
it is the result of radiation at all levels in the field of view.  Knowing the
weighting function for the wavelength bands you have imagery for will help 
define
where the majority of the energy is coming from.

re: out of curiosity, how does that algorithm determine cloud top pressure from 
a
single band?

> This is the information of their algorithm available on their website:
> 
> Visible Infrared Solar-Infrared Split Window Technique (VISST)
> 
> + Algorithm
> - Daytime
> - 0.65, 3.9, 10.8, 12.0 µm channels
> - Utilizes parameterization of theoretical radiance calculations for 7 water
>   and 9 ice crystal size distributions
> - Retrieves cloud optical properties by matching calculations to observations
> 
> + Required Inputs
> - Atmospheric profiles from model runs or in situ measurements
> - Surface characterization from IGBP 10 minute map
> - Uses CERES cloud mask algorithm
> - Clear sky reflectances from CERES
> - Narrowband to Broadband flux conversion functions
> - Satellite data (GOES 8-10, 12; 4-km: AVHRR, 1 or 4-km)
> 
> + Products
> - Pixel-level and gridded cloud properties (t, Re, LWP, IWP, Phase, etc)
> 
> + Domains
> - ARM SGP, ARM TWP, CONUS East and West

Very good.  This synopsizes in a much better way what I was trying to say -- one
needs a LOT more than just one satellite image band to deduce cloud parameters
like base/top heights/pressures, etc.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: OXG-395498
Department: Support McIDAS
Priority: Normal
Status: Closed